/*
 * Userland implementation of gettimeofday() for 32 bits processes in a
 * ppc64 kernel for use in the vDSO
 *
 * Copyright (C) 2004 Benjamin Herrenschmuidt (benh@kernel.crashing.org,
 *                    IBM Corp.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */
#include <asm/processor.h>
#include <asm/ppc_asm.h>
#include <asm/vdso.h>
#include <asm/asm-offsets.h>
#include <asm/unistd.h>

/* Offset for the low 32-bit part of a field of long type */
#ifdef CONFIG_PPC64
#define LOPART  4
#define TSPEC_TV_SEC    TSPC64_TV_SEC+LOPART
#else
#define LOPART  0
#define TSPEC_TV_SEC    TSPC32_TV_SEC
#endif

        .text
/*
 * Exact prototype of gettimeofday
 *
 * int __kernel_gettimeofday(struct timeval *tv, struct timezone *tz);
 *
 */
V_FUNCTION_BEGIN(__kernel_gettimeofday)
  .cfi_startproc
        mflr    r12
  .cfi_register lr,r12

        mr      r10,r3                  /* r10 saves tv */
        mr      r11,r4                  /* r11 saves tz */
        bl      __get_datapage@local    /* get data page */
        mr      r9, r3                  /* datapage ptr in r9 */
        cmplwi  r10,0                   /* check if tv is NULL */
        beq     3f
        lis     r7,1000000@ha           /* load up USEC_PER_SEC */
        addi    r7,r7,1000000@l         /* so we get microseconds in r4 */
        bl      __do_get_tspec@local    /* get sec/usec from tb & kernel */
        stw     r3,TVAL32_TV_SEC(r10)
        stw     r4,TVAL32_TV_USEC(r10)

3:      cmplwi  r11,0                   /* check if tz is NULL */
        beq     1f
        lwz     r4,CFG_TZ_MINUTEWEST(r9)/* fill tz */
        lwz     r5,CFG_TZ_DSTTIME(r9)
        stw     r4,TZONE_TZ_MINWEST(r11)
        stw     r5,TZONE_TZ_DSTTIME(r11)

1:      mtlr    r12
        crclr   cr0*4+so
        li      r3,0
        blr
  .cfi_endproc
V_FUNCTION_END(__kernel_gettimeofday)

/*
 * Exact prototype of clock_gettime()
 *
 * int __kernel_clock_gettime(clockid_t clock_id, struct timespec *tp);
 *
 */
V_FUNCTION_BEGIN(__kernel_clock_gettime)
  .cfi_startproc
        /* Check for supported clock IDs */
        cmpli   cr0,r3,CLOCK_REALTIME
        cmpli   cr1,r3,CLOCK_MONOTONIC
        cror    cr0*4+eq,cr0*4+eq,cr1*4+eq
        bne     cr0,99f

        mflr    r12                     /* r12 saves lr */
  .cfi_register lr,r12
        mr      r11,r4                  /* r11 saves tp */
        bl      __get_datapage@local    /* get data page */
        mr      r9,r3                   /* datapage ptr in r9 */
        lis     r7,NSEC_PER_SEC@h       /* want nanoseconds */
        ori     r7,r7,NSEC_PER_SEC@l
50:     bl      __do_get_tspec@local    /* get sec/nsec from tb & kernel */
        bne     cr1,80f                 /* not monotonic -> all done */

        /*
         * CLOCK_MONOTONIC
         */

        /* now we must fixup using wall to monotonic. We need to snapshot
         * that value and do the counter trick again. Fortunately, we still
         * have the counter value in r8 that was returned by __do_get_xsec.
         * At this point, r3,r4 contain our sec/nsec values, r5 and r6
         * can be used, r7 contains NSEC_PER_SEC.
         */

        lwz     r5,WTOM_CLOCK_SEC(r9)
        lwz     r6,WTOM_CLOCK_NSEC(r9)

        /* We now have our offset in r5,r6. We create a fake dependency
         * on that value and re-check the counter
         */
        or      r0,r6,r5
        xor     r0,r0,r0
        add     r9,r9,r0
        lwz     r0,(CFG_TB_UPDATE_COUNT+LOPART)(r9)
        cmpl    cr0,r8,r0               /* check if updated */
        bne-    50b

        /* Calculate and store result. Note that this mimics the C code,
         * which may cause funny results if nsec goes negative... is that
         * possible at all ?
         */
        add     r3,r3,r5
        add     r4,r4,r6
        cmpw    cr0,r4,r7
        cmpwi   cr1,r4,0
        blt     1f
        subf    r4,r7,r4
        addi    r3,r3,1
1:      bge     cr1,80f
        addi    r3,r3,-1
        add     r4,r4,r7

80:     stw     r3,TSPC32_TV_SEC(r11)
        stw     r4,TSPC32_TV_NSEC(r11)

        mtlr    r12
        crclr   cr0*4+so
        li      r3,0
        blr

        /*
         * syscall fallback
         */
99:
        li      r0,__NR_clock_gettime
        sc
        blr
  .cfi_endproc
V_FUNCTION_END(__kernel_clock_gettime)


/*
 * Exact prototype of clock_getres()
 *
 * int __kernel_clock_getres(clockid_t clock_id, struct timespec *res);
 *
 */
V_FUNCTION_BEGIN(__kernel_clock_getres)
  .cfi_startproc
        /* Check for supported clock IDs */
        cmpwi   cr0,r3,CLOCK_REALTIME
        cmpwi   cr1,r3,CLOCK_MONOTONIC
        cror    cr0*4+eq,cr0*4+eq,cr1*4+eq
        bne     cr0,99f

        li      r3,0
        cmpli   cr0,r4,0
        crclr   cr0*4+so
        beqlr
        lis     r5,CLOCK_REALTIME_RES@h
        ori     r5,r5,CLOCK_REALTIME_RES@l
        stw     r3,TSPC32_TV_SEC(r4)
        stw     r5,TSPC32_TV_NSEC(r4)
        blr

        /*
         * syscall fallback
         */
99:
        li      r0,__NR_clock_getres
        sc
        blr
  .cfi_endproc
V_FUNCTION_END(__kernel_clock_getres)


/*
 * Exact prototype of time()
 *
 * time_t time(time *t);
 *
 */
V_FUNCTION_BEGIN(__kernel_time)
  .cfi_startproc
        mflr    r12
  .cfi_register lr,r12

        mr      r11,r3                  /* r11 holds t */
        bl      __get_datapage@local
        mr      r9, r3                  /* datapage ptr in r9 */

        lwz     r3,STAMP_XTIME+TSPEC_TV_SEC(r9)

        cmplwi  r11,0                   /* check if t is NULL */
        beq     2f
        stw     r3,0(r11)               /* store result at *t */
2:      mtlr    r12
        crclr   cr0*4+so
        blr
  .cfi_endproc
V_FUNCTION_END(__kernel_time)

/*
 * This is the core of clock_gettime() and gettimeofday(),
 * it returns the current time in r3 (seconds) and r4.
 * On entry, r7 gives the resolution of r4, either USEC_PER_SEC
 * or NSEC_PER_SEC, giving r4 in microseconds or nanoseconds.
 * It expects the datapage ptr in r9 and doesn't clobber it.
 * It clobbers r0, r5 and r6.
 * On return, r8 contains the counter value that can be reused.
 * This clobbers cr0 but not any other cr field.
 */
__do_get_tspec:
  .cfi_startproc
        /* Check for update count & load values. We use the low
         * order 32 bits of the update count
         */
1:      lwz     r8,(CFG_TB_UPDATE_COUNT+LOPART)(r9)
        andi.   r0,r8,1                 /* pending update ? loop */
        bne-    1b
        xor     r0,r8,r8                /* create dependency */
        add     r9,r9,r0

        /* Load orig stamp (offset to TB) */
        lwz     r5,CFG_TB_ORIG_STAMP(r9)
        lwz     r6,(CFG_TB_ORIG_STAMP+4)(r9)

        /* Get a stable TB value */
2:      mfspr   r3, SPRN_TBRU
        mfspr   r4, SPRN_TBRL
        mfspr   r0, SPRN_TBRU
        cmplw   cr0,r3,r0
        bne-    2b

        /* Subtract tb orig stamp and shift left 12 bits.
         */
        subfc   r4,r6,r4
        subfe   r0,r5,r3
        slwi    r0,r0,12
        rlwimi. r0,r4,12,20,31
        slwi    r4,r4,12

        /*
         * Load scale factor & do multiplication.
         * We only use the high 32 bits of the tb_to_xs value.
         * Even with a 1GHz timebase clock, the high 32 bits of
         * tb_to_xs will be at least 4 million, so the error from
         * ignoring the low 32 bits will be no more than 0.25ppm.
         * The error will just make the clock run very very slightly
         * slow until the next time the kernel updates the VDSO data,
         * at which point the clock will catch up to the kernel's value,
         * so there is no long-term error accumulation.
         */
        lwz     r5,CFG_TB_TO_XS(r9)     /* load values */
        mulhwu  r4,r4,r5
        li      r3,0

        beq+    4f                      /* skip high part computation if 0 */
        mulhwu  r3,r0,r5
        mullw   r5,r0,r5
        addc    r4,r4,r5
        addze   r3,r3
4:
        /* At this point, we have seconds since the xtime stamp
         * as a 32.32 fixed-point number in r3 and r4.
         * Load & add the xtime stamp.
         */
        lwz     r5,STAMP_XTIME+TSPEC_TV_SEC(r9)
        lwz     r6,STAMP_SEC_FRAC(r9)
        addc    r4,r4,r6
        adde    r3,r3,r5

        /* We create a fake dependency on the result in r3/r4
         * and re-check the counter
         */
        or      r6,r4,r3
        xor     r0,r6,r6
        add     r9,r9,r0
        lwz     r0,(CFG_TB_UPDATE_COUNT+LOPART)(r9)
        cmplw   cr0,r8,r0               /* check if updated */
        bne-    1b

        mulhwu  r4,r4,r7                /* convert to micro or nanoseconds */

        blr
  .cfi_endproc